Limb immobilisers and braces for limbs and joints are well known. An immobiliser may consist of nothing more complex than a relatively rigid member bound to a limb with tape or bandages, or it may be more elaborate with numerous reinforcements, flaps, pads, and pockets.
Braces, such as knee braces, also are available in many types and varying degrees of complexity. Several are described in co-owned UK patent GB 2,130,488B, U.S. Pat. Nos. 4,467,792 and 4,559,935, and European patent 0109847. A further detailed discussion of the art is given in published UK specification GB 2,182,714A. A modular bracing system is also disclosed in co-owned published application GB 2,177,603B and U.S. Pat. No. 4,776,326.
We are also aware of a knee brace marketed by DePuy Inc. of Warsaw, Ind., U.S.A., that has medial and lateral hinges and proximal and distal hinge arms. A leg-contacting shell is carried by each of the arms with the calf shells being fixed in place but the thigh shells being slidably connected to the proximal arms. Specifically, a hole near the upper end of each proximal arm is threaded and each thigh shell has a central slot extending along a part of the length thereof. A turnscrew is slidably retained in the slot and can be tightened to lock each thigh shell in a selected position along the proximal arm on which it is mounted.
A knee brace by Zimmer Incorporated of Charlotte, N.C., U.S.A., marketed as the "LM 10" brace, also utilizes the slotted sliding shell principle. In both the DePuy and Zimmer braces, the shells appear to be of relatively thin plastics material and the provision of slots, for slidable attachment to the proximal arms, increases their weakness. In addition, both braces use circumferential hook and loop material straps to secure them to patients. A disadvantage of such a strapping system is that a brace may move or "gape" under the straps during flexion; this amounts to failure of the brace to exert control of the joint. Immobilisers with such strapping systems are also liable to be overridden by strong vigorous patients.
Another disadvantage of existing constructions is that the attachment straps are commonly connected to edge portions of the flexible shells. Tensioning of the straps may result in an undesirable application of forces transmitted to and by certain portions of the shells and also to the possibility that such tensioning, either during application or wearer movement, may result in shell failure.
An important aspect of this invention therefore lies in providing an adjustable immobiliser or brace in which the shells or limb-contacting plates may be easily extended or retracted without, at the same time, resulting in a construction that presents a substantial risk of failure under conditions of vigorous use. Donning and doffing of the device may be easily and quickly achieved without requiring the wearer to step into or through the device.
A particularly important aspect of the invention lies in providing an adjustable brace/immobiliser construction in which loadings are distributed and are not directly applied by the attachment straps to the edges of the limb-contacting plates or shells. Instead, flexible traction plates are joined directly to the straps and in turn exert centrally-directed forces against the limb-contacting plates which then distribute those forces against medial and lateral surfaces of the limb. While the anterior/posterior edges of the limb-contacting plates do not function as strap-attachment zones, they may nevertheless perform a protective function in shielding the limb against direct contact by the tensioned straps.
Briefly, a limb brace or immobiliser embodying this invention includes at least two relatively rigid support arms adapted to extend medially and laterally along opposite sides of a wearer's limb in the vicinity of a joint. In the case of a brace, the support arms are connected to hinges along with a second set of support arms, thereby permitting controlled movement at the joint, whereas in the case of an immobiliser, the support arms are unjointed and, when worn by a patient, lock the joint against flexion and extension. Whether the invention is utilized with a limb brace or a limb immobiliser, there must be at least one medial limb support arm and at least one lateral limb support arm.
First and second limb-contacting plates of arcuate cross-sectional configuration are connected to the two support arms. At least two traction plates, which may also be referred to as drawbar plates, are associated with the limb-contacting plates, each traction plate having a pair of wing portions extending anteriorly and posteriorly with respect to a limb support arm and being spaced outwardly from the limb-contacting plate associated therewith. The span of the wing portions of each traction plate is substantially less than the anterior-posterior dimension of the associated limb-contacting plate. Attachment straps are adjustably secured to the wing portions and join corresponding wing portions of the traction plates on opposite sides of a wearer's limb to secure the assembly in limb-bracing or limb-immobilising condition. Since each traction plate is centrally joined to or merged with a limb-contacting plate, forces exerted by the tightened straps are applied centrally to the limb-contacting plates and are then distributed against the limb by the flexible limb-contacting plates. The traction plates are most advantageously formed of stiff but flexible thermoplastic material so that their wing portions, which normally angle outwardly away from the central portions, may flex inwardly under the tensioning forces applied by the straps. Flexure of the wing portions, and their capability of returning to their original positions when tensioning forces are wholly or partially relieved, results in a cushioning action that helps maintain the brace/immobiliser in position without excessive tightening of the straps. Since the anterior/posterior edges of the traction plates are spaced well inboard from the edges of the associated limb-contacting plates, the limb-contacting plates may perform a shielding function in preventing or reducing direct contact between the attachment straps and the patient's limb.
Other features, advantages, and objects of the invention will become apparent from the specification and drawings.